Finite element simulation of resistance welding requires coupling between mechanical, thermal and... more Finite element simulation of resistance welding requires coupling between mechanical, thermal and electrical models. This paper presents the numerical models and their couplings that are utilized in the computer program SORPAS. A mechanical model based on the irreducible flow formulation is utilized to simulate plastic deformation and the resulting distribution of stress, a thermal model based on transient heat transfer is used to determine the distribution of temperature, and a steady-state electrical model is employed to calculate the distribution of electrical potential and current density. From a resistance welding point of view, the most essential coupling between the above mentioned models is the heat generation by electrical current due to Joule heating. The interaction between multiple objects is another critical feature of the numerical simulation of resistance welding because it influences the contact area and the distribution of contact pressure. The numerical simulation ...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2014
This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects ... more This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects of finite element implementation and three-dimensional modelling of resistance welding. A new simulation environment is proposed in order to perform three-dimensional simulations and optimization of resistance welding together with the simulations of conventional and special-purpose quasi-static mechanical tests. Three-dimensional simulations of resistance welding consider the electrical, thermal, mechanical and metallurgical characteristics of the material as well as the operating conditions of the welding machines. Simulations of the mechanical tests take into account material softening due to the accumulation of ductile damage and cover conventional tests, such as tensile–shear tests, cross-tension test and peel tests, as well as the possibility of special-purpose tests designed by the users. The overall presentation is supported by numerical simulations of electrode misalignment caus...
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2017
This paper presents a new approach based on a fully coupled procedure in which the lubricant flow... more This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and the plastic deformation of the metallic material in metal forming are solved simultaneously. The proposed method is an alternative to conventional modelling techniques which allow studying the effect of a broad range of parameters directly on the friction conditions. The approach is applied to strip reduction of a sheet with mesoscopic surface pockets in order to investigate the escape of lubricant from the pocket by means of Micro Plasto HydroDynamic Lubrication and Micro Plasto HydroStatic Lubrication. For the investigation on Micro Plasto HydroStatic Lubrication, the friction along the tool–workpiece contact interface and the back tension are taken as parameters, and the backward escape Micro Plasto HydroDynamic Lubrication is investigated by variations in lubricant viscosity by means of a combined numerical and analytical model, and by variations in drawing speed. Good agreement...
While texturing of workpiece surfaces to promote lubrication in metal forming has been applied fo... more While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades tool surface texturing is rather new. In the present paper tool texturing is studied as a method to prevent galling. Adopting a strip reduction test longitudinal pocket geometries oriented perpendicular to the sliding direction, with shallow pocket depth, small pocket angle to the workpiece surface and varying distance between pockets are investigated. The experiments reveal that the distance between pockets should be larger than the pocket width thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise an increase in drawing load and pick-up on the tools is observed. The textured tool surface lowers friction and improves lubrication performance provided that the distance between pockets is 2-4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pocke...
The Journal of Strain Analysis for Engineering Design, 2009
Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process t... more Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large e...
Finite element simulation of resistance welding requires coupling between mechanical, thermal and... more Finite element simulation of resistance welding requires coupling between mechanical, thermal and electrical models. This paper presents the numerical models and their couplings that are utilized in the computer program SORPAS. A mechanical model based on the irreducible flow formulation is utilized to simulate plastic deformation and the resulting distribution of stress, a thermal model based on transient heat transfer is used to determine the distribution of temperature, and a steady-state electrical model is employed to calculate the distribution of electrical potential and current density. From a resistance welding point of view, the most essential coupling between the above mentioned models is the heat generation by electrical current due to Joule heating. The interaction between multiple objects is another critical feature of the numerical simulation of resistance welding because it influences the contact area and the distribution of contact pressure. The numerical simulation ...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2014
This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects ... more This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects of finite element implementation and three-dimensional modelling of resistance welding. A new simulation environment is proposed in order to perform three-dimensional simulations and optimization of resistance welding together with the simulations of conventional and special-purpose quasi-static mechanical tests. Three-dimensional simulations of resistance welding consider the electrical, thermal, mechanical and metallurgical characteristics of the material as well as the operating conditions of the welding machines. Simulations of the mechanical tests take into account material softening due to the accumulation of ductile damage and cover conventional tests, such as tensile–shear tests, cross-tension test and peel tests, as well as the possibility of special-purpose tests designed by the users. The overall presentation is supported by numerical simulations of electrode misalignment caus...
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2017
This paper presents a new approach based on a fully coupled procedure in which the lubricant flow... more This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and the plastic deformation of the metallic material in metal forming are solved simultaneously. The proposed method is an alternative to conventional modelling techniques which allow studying the effect of a broad range of parameters directly on the friction conditions. The approach is applied to strip reduction of a sheet with mesoscopic surface pockets in order to investigate the escape of lubricant from the pocket by means of Micro Plasto HydroDynamic Lubrication and Micro Plasto HydroStatic Lubrication. For the investigation on Micro Plasto HydroStatic Lubrication, the friction along the tool–workpiece contact interface and the back tension are taken as parameters, and the backward escape Micro Plasto HydroDynamic Lubrication is investigated by variations in lubricant viscosity by means of a combined numerical and analytical model, and by variations in drawing speed. Good agreement...
While texturing of workpiece surfaces to promote lubrication in metal forming has been applied fo... more While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades tool surface texturing is rather new. In the present paper tool texturing is studied as a method to prevent galling. Adopting a strip reduction test longitudinal pocket geometries oriented perpendicular to the sliding direction, with shallow pocket depth, small pocket angle to the workpiece surface and varying distance between pockets are investigated. The experiments reveal that the distance between pockets should be larger than the pocket width thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise an increase in drawing load and pick-up on the tools is observed. The textured tool surface lowers friction and improves lubrication performance provided that the distance between pockets is 2-4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pocke...
The Journal of Strain Analysis for Engineering Design, 2009
Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process t... more Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large e...
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